The Rocket claimed the encounter took place at a city centre restaurant on Saturday while he was having lunch and a coffee with friends in between the morning and evening sessions.
He will now cut back his appearances in public to minimise the risk of being forced to withdraw due to a positive test later in the tournament – after he previously called for protection from “over-excited fans or someone who might have had a drink that wants to get in your space."
O’Sullivan, who said two members of the restaurant’s staff had been forced to intervene, said: “Ninety-nine per cent of the people are fine but it’s just the odd one who was a bit boozed up and having a mental one. It was so busy and this geezer was a nightmare.
“He was p***ed up and coming at me and I was like, ‘mate, please.’ What can you do? I’ve got to stay indoors and stay away.
“If I didn’t have to be clean for this tournament it wouldn’t matter, but if I reached the quarter-finals it would be a sickener to have to pull out. As a sportsman I can’t work if I get ill so that’s my only problem.”
Sheffield city centre was busier than it had been for months on Saturday as people flocked back to pubs, bars and restaurants for outdoor service as well as non-essential retail shops, hairdressers and beauty salons.
Hundreds of protestors also took part in another ‘Kill the Bill’ demonstration on Saturday afternoon, which passed by The Crucible and briefly stopped outside the Winter Garden.
Nevertheless O’Sullivan hailed the return of fans to the famous venue, which was filled to 33 per cent capacity as part of a pilot scheme surrounding the return of fans to sporting events, after winning his first match.
He added: “It was great to have the crowd in there, they miss their snooker and I probably would have given up mentally in that match if there was no crowd there.”
O’Sullivan will be back in action on Thursday afternoon against either Anthony McGill or Ricky Walden.